Heat treatment apparatus



Dec. 14, 1965 A. W. THOMPSON HEAT TREATMENT APPARATUS Filed April 22, 1963 2 Sheets-Sheet 1 Dec. 14, 1965 A. w. -rHoMPsoN 3,223,396

HEAT TREATMENT APPARATUS Filed April 22, 1963 2 Sheets-Sheet 2 INVENTOR. /Jf?? Wjaz/vsaz iffaf Waff.

United States Patent O 3,223,396 HEAT TREATMENT APPARATUS Alden W. Thompson, Cranston, RJ., assignor to C. I. Hayes, Inc., Cranston, RJ., a corporation of Rhode island Filed Apr. 22, 1963, Ser. No. 274,502 3 Claims. (Cl. 26a- 5) The present invention relates to heat treatment apparatus. More particularly, the present invention relates to apparatus of the type that is utilized in connection with the heat treatment of high-speed steels, stainless steels and the like.

The heat treatment apparatus embodied in the present invention includes a furnace construction that is normally associated with the heat treatment of metals that are moved continuously through the heat treatment chambers thereof. In the heat treatment of continuously moving work loads that are feeding through a heating chamber, the ends of the heat chamber are normally open to receive the continuously moving work load or pieces. Prior to the instant invention, it has been the practice to provide some form of curtain, such as a flame curtain, that is located at the entrance and exit sides of the heat treatment chamber for preventing the inflow of atmospheric air into the heat treatment chamber. Flame curtains have been found to be objectionable; since the flame creates water vapor, causes carbon deposits to appear on the work pieces, and otherwise provides additional heat for the work that is objectionable. The present invention eliminates the prior known flame curtain and provides for a barrier or curtain dened by an inert gas that is ntroduced into the passageway through which the work piece passes and exteriorly of the heat treatment chamber. By introducing the inert gas into lthe passageway through which the work piece or load passes under pressure, the open end of the passageway is effectively sealed from the interior of the heat treatment chamber, and atmospheric air is prevented from entering the heat treatment chamber and contaminating the work piece or load being heat treated therein.

The present invention also contemplates the use of a heat treatment atmosphere, controlled amounts of which are introduced into the heat treatment chamber, for maintaining required controlled conditions therein. Since it is necessary to provide a continuous flow of heat treatment atmosphere, some means must be provided for discharging this atmosphere from the heat treatment chamber and the furnace construction. In the present invention, a burnotf stack is provided wherein the hydrogen associated with the heat treatment atmosphere is burned oif in a continuous flame at the uppermost end of the stack and the volatile materials are trapped below the flame by means of a tive stream that is positioned within the stack. The system embodied in the present invention, therefore, contemplates the introduction of the inert gas to dene an air curtain for preventing the ingress of atmospheric air into a heat treatment chamber and further includes means for burning off the heat treatment atmosphere, the air curtain being located in close proximity to the stack so that if the flame burns out, the inert gas that forms the gas curtain can be utilized to prevent air from circulating into the heat treatment chamber by way of the stack. It is, of course, essential to prevent the introduction of atmospheric air into the heat treatment chamber in order to prevent Contamination and possible explosions.

Accordingly, it is an object of the present invention to provide heat treatment apparatus that incorporates a gas barrier for prevention of introduction of atmospheric air into the heat treatment chamber thereof.

Another object of the present invention is to provide a ICC heat treatment furnace wherein a controlled treatment atmosphere is circulated through the heat treatment chamber and is discharged through a burn-olf stack.

Still another object is to provide a gas curtain for use in the passageway of a heat treatment furnace, the gas curtain being created by the ejection of an inert gas under pressure into the passageway and toward an open end thereof.

Still another object is to provide a burn-01T stack for use with heat treatment apparatus that is located in close proximity to an air curtain so that if the ame of the burn-oit stack should fail, the air curtain would prevent the introduction of atmospheric air into the heat chamber of the furnace construction.

Other objects, features and advantages of the invention will become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.

In the drawings which illustrate the best mode presently contemplated for carrying out the instant invention:

FIG. 1 is a vertical sectional view of a passageway that communicates with the heat treatment chamber of a furnace construction and further showing the location of a barrier gas ejection system and a burn-olf stack located in close proximity thereto;

FIG. 2 is a vertical sectional view of the apparatus illustrated in FIG. 1 but rotated 90 with respect thereto;

FIG. 3 is a top plan View of the apparatus illustrated in FIGS. 1 and 2;

FIG. 4 is a perspective view of the passageway and burn-oit stack illustrated in FIG. 1 and showing the relationship thereof with respect to the hea-t treatment chamber of the furnace construction;

FIG. 5 is a fragmentary enlarged sectional view showing the location of the nozzles with respect to the manifold of the gas barrier ejection system;

FIG. 6 is a sectional view taken along lines 6 6 in FIG. 5;

FIG. 7 is a sectional view taken along lines 7-7 in FIG. 1; and

FIG. 8 is a top plan view of the re screen located at the uppermost end of the burn-olf stack.

Referring now to the drawings and particularly to FIG. 4, a portion of the furnace construction embodied herein is illustrated, the furnace construction being generally indicated at 10. For purposes of illustration, the heat treatment chamber is generally indicated at 12, it being understood that the heat treatment chamber 12 is constructed in conventional fashion for the purpose of heat treating metal pieces therein, such as high speed steels, stainless steels, and the like. The present invention has particular application in the heat treatment of work pieces that are moved continuously through the heat treatment chamber 12, this continuous movement being carried out through a belt construction or the like that is also conventional in furnace constructions of this type. It lis understood, of course, that the concept of the invention may also be employed in the batch type furnace wherein a sliding door is disposed at an end of the furnace construction to cover the inl-et opening thereof.

In the furnace construction of the present invention, an inlet opening to the heat treatment chamber 12 is indicated at 14, an outlet opening or discharge opening being located on the opposite side of the heat treatment chamber 12 but not shown herein. It will be further understood that the concept of the invention embodied herein may be incorporated in connection with either the inlet opening 14 or the exhaust opening (not shown), as will be more apparent from the following description.` As illustrated in FIG. 4, an inlet housing 16 that is substantially rectangular in cross sectional configuration is joined to the heat treatment chamber 12 anddenes an inlet passageway 18 that communicates with the inlet opening 14 of the heat chamber 12. The work to be heat treated is normally introduced into the heat chamber 12 by a continuously moving belt (not shown) that carries the work through the passageway 18 and inlet opening 14 into the interior of the heat chamber 12. The direction of movement of the work is illustrated by the arrow in FIG. 4. The corresponding outlet communicating with the heat chamber 12 is constructed similarly to the inlet housing 16 and is formed with a passageway through which the work travels after it is discharged from the heat chamber 12 by the continuously moving belt.

Since the passageway 18 of the inlet housing 16 is open to atmosphere at the outer end thereof, it is necessary to prevent the ingress of atmospheric air into the chamber 12. For this purpose, a gas barrier is provided, the gas barrier being dened by an inert gas that is ejected into the passageway 18 under pressure and in the direction of the opening to the passageway.

Referring now to FIGS. 1, 2 and 4, the particular constructional arrangement for ejecting the gas barrier into the passageway 18 is illustrated and, as shown, includes a vertically extending conduit 20 that is disposed internally of a cylindrical stack 22 that is secured directly to the upper wall of the inlet housing 16 and that has communication with the passageway 18 through an opening 24. As will be described in more detail hereinafter, the stack 22 is utilized for discharging the heat treatment atmosphere by burning off certain components thereof at the upper open end of the stack.

The inlet gas conduit 20 is formed with a lower section 26 that extends through the opening 24 of the housing 18 and also includes an upper section 28 that has an elbow configuration and that extends through the wall of the stack 22. The upper section 28 is threaded at the exposed end thereof, as indicated at 27, and receives a coupling 29 in threaded relation thereon. The coupling 29 is mounted on a reduced conduit 30 that is joined directly to the outlet of a ow meter 32, an inlet conduit 34 being joined to the inlet side of the ow meter 32 and being further connected to a source of an inert gas, such as nitrogen, helium, argon, etc. It will be understood that the inert gas isintroduced into the conduit 20 by means of the inlet conduit 34, ow meter 32, reduced conduit 30, coupling 29 and upper section 28 of the conduit 20.

Joined directly to the lower section 26 of the conduit 20 and located interiorly of the inlet housing 16, extending transversely with respect thereto, is a manifold 36. As shown more clearly in FIGS. l, 2, and 6, the manifold 36 is located adjacent the upper wall of the inlet housing 16 and extends substantially the width thereof. A deector 38 is located within the manifold 36 just below the intersection of the manifold with respect to the conduit 20 and is adapted to direct the incoming gas to the opposite portions of the manifold. Formed in the manifold are a plurality of nozzles 40 which, as shown in FIGS. 2, 5 and 6 are formed in adjacent rows in the manifold 36. One row of the nozzles 40 is located adjacent the front of the manifold 36, each front nozzle 40 being positioned such that the axis thereof defines an angle of 30 with respect to the vertical. The forwardly facing nozzles 40 thus direct the gas ejected therethrough at an angle of 30 to the vertical and toward the open end of the passageway 18. The other row of nozzles 41 are located adjacent the rear of the manifold 36, each rear nozzle 41 being positioned such that the axis thereof defines an angle of with respect to the vertical. The rearwardly facing nozzles 41 thus direct the gas ejected therethrough at an angle of 15 to the vertical and toward the rear of the passageway 18. The rearwardly directed gas stream thereby acts to form an inert gas barrier in the area below the stack 22 for inhibiting the heat treatment atmosphere from owng toward the open end of the passageway 18. Both sets of the nozzles 40 are disposed in spaced-apart relation `substantially the width of the passageway 18 and are thus adapted to eject the inert gas into the passageway so as to substantially envelop the passageway to form a gas curtain therein. As shown in FIG. 6, the position of the rearwardly facing nozzles 41 is staggered with respect to the forwardly facing nozzles 40.

As mentioned hereinabove, the stack 22 is provided for burning off the heat treatment atmosphere that is circulated within the heat treatment chamber 12 during the heat treatment of the work within the chamber. The purpose of using such an atmosphere is to prevent contamination of the work when it is subjected to relatively high heat heat treatment temperatures, which contamination would occur if air or any other impure or non-humidified atmosphere were present in the heat treatment chamber. It is standard practice in the operation of industrial heat treatment furnaces to maintain a steady ow of a carefully controlled and dried atmosphere through the heat treatment chamber of the furnace, the flow of the heat treatment atmosphere normally serving to prevent the ingress of air or other impure atmospheres into the heating chamber of the furnace where contamination of the work is most likely to occur. In the present invention, use of the heat treatment atmosphere for preventing contamination of the work within the furnace is supplemented by the use of the gas barrier as described, thereby insuring that air will not reach the heat treatment chamber during the heat treatment Operation. Since there is a continuous ow of heat treatment atmosphere through the heat treatment chamber, some provision must be made for continuously discharging this atmosphere from the chamber. For this purpose, the stack 22 is provided, and, as shown in FIGS. 1, 2 and 4, the stack 22 is mounted on the upper wall of the inlet housing 16 for communication with the interior of the heat treatment chamber 12 by way of the passageway 18 and the inlet opening 14. Referring particularly to FIGS. 1 and 2, the stack 22 is shown comprising an elongated tubular member 42 that is secured at the lowermost end thereof to a plate 44. The plate 44 is secured to anges 46 and 48 by bolts 50, the flanges 46 and 48 being joined to the side walls of the inlet housing 16 by welding or the like. As shown more clearly in FIG. 1, a silicone type washer or gasket 52 is disposed between the plate 44 and the flanges 46, 48 so as to effectively seal the plate 44 in position on the housing 16 and thereby preventing air leakage within the housing. It is understood, of course, that the plate 44 is also formed with an opening 53 that generally corresponds to the opening 24, thereby providing for communication of the stack 22 with the passageway 18 of the inlet housing 16.

As mentioned hereinabove, the stack 22 is provided for discharging the heat treatment atmosphere from the chamber 12. Since a component of the heat treatment atmosphere is burned off at the top of the stack, some provision must be made for screening the interior portions of the stack. For this purpose, a tire screen 54 is provided and, as shown in FIGS. 1 and 2, the fire screen 54- has an inverted cone shape lconfiguration and is secured to the uppermost end of the tubular member 42 of the stack. In order to removably mount the fire scr'een in position, the uppermost ends of the fire screen 54 are folded over the adjacent uppermost edge of the tubular member 42, and a cap 56 formed with a depending skirt and an opening 58 therein that communicates with the interior of the tubular member 42 is placed over the folded edges of the fire screen to lock the screen in place.

As illustrated in FIG. 4, the heat treatment atmosphere is discharged from the heat chamber 12 through the inlet opening 14 and flows upwardly through the stack 22 as indicated by the arrows. Normally the heat treatment atmosphere is dissociated ammonia, and accordingly, it is desirable to burn olf the hydrogen component of the dissociated ammonia. By providing a pilot (not shown), a llame may be produced as indicated in the dotted lines at 60 in FIG. 4 at the upper exposed end of the stack 22, the flame being caused by the continuous burning olf of the hydrogen of the heat treatment atmosphere that flows upwardly through the stack 22. The lire screen S4 is adapted to collect the volatile materials of the heat treatment atmosphere, the hydrogen of the heat treatment atmosphere being lighter than the volatile materials and thereby passing upwardly through the fire screen 54 and being burned off at the top of the stack. The fire screen 54 not vonly collects the volatile materials of the heat treatment atmosphere, but also acts to break up the flame and thereby prevents flame backup within the vstach 22. The continuously burning dame and the lire screen 54 thus cooperate to prevent any air leakage from entering the inlet passageway 16 and inlet opening 14 by way of the stack 22.

As described hereinabove, the inlet conduit 2@ for the gas barrier or curtain is located within the stack 22, the nozles 40 of the manifold 36 being disposed directly beneath the lowermost end of the stack 22. By providing this constructional arrangement wherein the inlet conduit and the ejection nozzles il are located closely adjacent the stack 22, in the event of flame burnout a small portion of the inert gas that is ejected through the nozzles 41B will have a tendency to back up into the stack 22. Thus the inert gas will tend to prevent the air from flowing inwardly from the top of the stack into the inlet passageway 1S and eventually into the heat treament chamber 12. Since a small portion of the inert gas does flow upwardly into the stack 22 at all times, the temperature -of the lower portions of the stack is reduced .so that no burning action takes place therein. By reason of this arrangement, all of the burning of the hydrogen is produced at the top of the stack in the burnout area above the tire screen 54.

It will also be noted that some portion of the hydrogen that is formed as part of the heat treatment atmosphere may sometimes mix with the inert gas curtain. However, this mixture of the gases is not objectionable since an inert forming gas is produced that is not harmful if it is introduced into the heat treatment chamber i2. It is seen that the heat treatment atmosphere that is continuously circulated within the heat treatment chamber 12 cooperates with the gas barrier that is ejected from the nozzles 40 to prevent the introduction of air into the heat treatment chamber. The ejection nozzles 40 may be spaced from the front edge of the inlet housing 16 as desired and depending upon the cr-oss sectional area of the inlet passageway 18. In other words, if the passageway 18 has a large cross sectional configuration, then it would be desirable to place the ejection nozzles 40 more closely adjacent the outer or exposed end of the inlet housing 16.

As pointed out hereinabove, the concept of the invention embodied herein is not limited to the location of the gas barrier at the inlet side of the heat treatment chamber 12. It is understood that a similar gas barrier may be employed on the discharge side of the heat treatment chamber, and it is further understood that a stack similar to the stack 22 may be located adjacent the gas barrier on the discharge side of the heat treatment chamber.

While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.

What is claimed is:

1. In a furnace for use in the heat treatment of a continuously moving work piece, a heat treatment chamber through which said work piece travels during the heat treatment thereof, a passageway open to atmosphere communicating with said chamber and through which said work piece passes, means for introducing a heat treatment atmosphere into said heat treatment chamber, a vertically extending stack communicating with said passageway and through which the heat treatment atmosphere is discharged and burned off after circulation through said heat treatment chamber, a conduit located in said stack and projecting downwardly therethrough, said conduit terminating directly beneath said stack and extending into said passageway, and means for introducing an inert gas under pressure into said conduit for passage therethrough into said passageway, said conduit directing the major portion of said inert gas toward the open end of said passageway to define a barrier for preventing atmospheric air from entering said heat treatment chamber from the entrance end of said passageway, a relatively small portion of the inert gas being directed upwardly from the lowermost end of said conduit into said stack for reducing the temperature of the lower end of said stack to prevent burning of treatment gas therein, said inert gas directed into said stack further preventing ingress of atmosphere into said passageway from said stack in the event that burn-out of said heat treatment atmosphere occurs at the upper end of said stack.

2. In a furnace as set forth in claim 1, a manifold joined to the lowermost end of said conduit and located in said passageway transversely thereof and directly beneath said stack.

3. In a furnace as set forth in claim 1, said conduit directing means consisting of a manifold including nozzles being formed in a forwardly facing row in said manifold and a rearwardly facing row therein, said forwardly facing nozzles being staggered with respect to said rearwardly facing nozzles and directing said inert gas toward the front of said passageway for preventing ingress of atmospheric air therein, the staggered rearwardly facing nozzles directing the inert gas toward the rear of said passageway to prevent discharge of said heat treatment atmosphere through the front of said passageway.

References Cited by the Examiner UNITED STATES PATENTS 890,252 6/1908 Thompson 263-3 1,778,876 10/1930 Weaver 48-192 FOREIGN PATENTS 478,879 1/1938 Great Britain.

WHITMORE A. WILTZ, Primary Examiner.

JAMES H. TAYMAN JR., MORRIS O. WOLK,

Examiners. 

1. IN A FURNACE FOR USE IN THE HEAT TREATMENT OF A CONTINUOUSLY MOVING WORK PIECE, A HEAT TREATMENT CHAMBER THROUGH WHICH SAID WORK PIECE TRAVELS DURING THE HEAT TREATMENT THEREOF, A PASSAGEWAY OPEN TO ATMOSPHERE COMMUNICATING WITH SAID CHAMBER AND THROUGH WHICH SAID WORK PIECE PASSES, MEANS FOR INTRODUCING A HEAT TREATMENT ATMOSPHERE INTO SAID HEAT TREATMENT CHAMBER, A VERTICALLY EXTENDING STACK COMMUNICATING WITH SAID PASSAGEWAY AND THROUGH WHITH THE HEAT TREATMENT ATMOSPHERE IS DISCHARGED AND BURNED OFF AFTER CIRCULATION THROUGH SAID HEAT TREATMENT CHAMBER, A CONDUIT LOCATED IN SAID STACK AND PROJECTING DOWNWARDLY THERETHROUGH, SAID CONDUIT TERMINATING DIRECTLY BENEATH SAID STACK AND AND EXTENDING INTO SAID PASSAGEWAY, AND MEANS FOR INTRODUCING AN INERT GAS UNDER PRESSURE INTO SAID CONDUIT FOR PASSAGE THERETHROUGH INTO SAID PASSAGEWAY, SAID CONDUIT DIRECTING THE MAJOR PORTION OF SAID INERT GAS TOWARD THE OPEN END OF SAID PASSAGEWAY TO DEFINE A BARRIER FOR PREVENTING ATMOSPHERIC AIR FROM ENTERING SAID HEAT TREATMENT CHAMBER FROM THE ENTRANCE END OF SAID PASSAGEWAY, A RELATIVELY SMALL PORTION OF THE INERT GAS BEING DIRECTED UPWARDLY FROM THE LOWERMOST END OF SAID CONDUIT INTO SAID STACK FOR REDUCING THE TEMPERATURE OF THE LOWER END OF SAID STACK FOR REDUCPREVENT BURNING OF TREATMENT GAS THEREIN, SAID INERT GAS DIRECTED INTO SAID STACK FURTHER PREVENTING INGRESS OF ATMOSPHERE INTO SAID PASSAGEWAY FROM SAID STACK IN THE EVENT THAT BURN-OUT OF SAID HEAT TREATMENT ATMOSPHERE OCCURS AT THE UPPER END OF SAID STACK. 